1. Field of the Invention
The present invention relates to a structure for cooling the cylinder head of a water-cooled multicylinder engine.
2. Description of the Relevant Art
Japanese Laid-Open Utility Model Publication No. 61-157144 discloses a structure for cooling the cylinder head of a water-cooled multicylinder engine.
The disclosed cylinder head has an array of cylinders defined therein. Exhaust valves are disposed on one side of cylinder head along the array of cylinders, and intake valves are disposed on the other side of the cylinder head. The cooling structure includes a water jacket positioned above the cylinders from said one side to the other side of the header head and extending along the cylinder array. The water jacket has therein partitions extending along the cylinder array and each disposed between adjacent two of the cylinders. Two adjacent partitions define therebetween a water jacket compartment located above one of the cylinders. Each water jacket compartment has cooling water inlet ports disposed near the exhaust valve and a cooling water outlet port disposed near the intake valve. A spark plug insertion tube is disposed in each of the water jacket compartments directly above the center of the corresponding cylinder.
In the cylinder head cooling structure, cooling water in the water jacket compartments associated with the respective cylinders first cools the valve seats for the exhaust valves and the exhaust passages extending from the exhaust valves, and then cools the bottom wall of the water jacket and the spark plug insertion tubes which are positioned above the respective cylinders. Thereafter, the cooling water cools the valve seats for the intake valves and the intake passages extending toward the intake valves.
Walls project from the partitions toward the spark plug insertion region in each of the water jacket compartments for guiding the cooling water toward the spark plug insertion tube when it passes over the cylinder, thereby efficiently cooling the spark plug insertion tube.
The present invention has been made in an effort to improve the aforesaid cylinder head cooling structure.